# OpenGL My first attempt with vertex pointers.

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Hello, I'm trying to figure out how to use vertex pointers with no luck... I have verified that all the loaded vertex data, vertices, colors, normals, uvs, and indices are correctly sent to this code:
/////////////// drawTrianglePointer /////////////
void pss::CGraphics_OpenGL::drawTrianglePointer(const SVertex* vertices, const unsigned short* indices, const int triangleCount)
{
if(! vertices || ! indices)
return;

glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_INDEX_ARRAY);

glVertexPointer(3,GL_FLOAT,sizeof(SVertex),&vertices[0].pos);
glNormalPointer(GL_FLOAT, sizeof(SVertex),&vertices[0].normals);
glTexCoordPointer(2,GL_FLOAT,sizeof(SVertex),&vertices[0].uv);
glColorPointer(4,GL_UNSIGNED_BYTE,sizeof(SVertex),&vertices[0].color);
glIndexPointer(GL_UNSIGNED_SHORT,0,indices);

glDrawElements(GL_TRIANGLES,triangleCount*3,GL_UNSIGNED_SHORT,indices);
glFlush();
}


However nothing is drawn to the screen. When I draw my test triangle using glBegin and glEnd however, something is drawn. I have checked the size of the model and adjusted the camera view so that the data should be in view, culling is turned off. So why doesn't it draw anything? According to my time logger I've been debugging this for over three hours, and I'm getting pretty upset. Thanks~ John DiSanti

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GL_INDEX_ARRAY and glIndexPointer are for color-indexed rendering (as in for 8-bit palette displays), not indicies into the vertex array. I agree -- the names are misleading :)

First try taking those two lines out and see what happens. Odds are since both the GL_COLOR_ARRAY and GL_INDEX_ARRAY are enabled, there's probably an error being thrown by glDrawElements.

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Shouldn't it be especially if pos, normals, uv and color are actually arrays. Notice the non-usage of reference.

glVertexPointer(3,GL_FLOAT,sizeof(SVertex),vertices[0].pos);glNormalPointer(GL_FLOAT, sizeof(SVertex),vertices[0].normals);glTexCoordPointer(2,GL_FLOAT,sizeof(SVertex),vertices[0].uv);glColorPointer(4,GL_UNSIGNED_BYTE, sizeof(SVertex),vertices[0].color);

And you shouldn't be needing to use the glIndexPointer.

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i think u need the reference cause u are giving the function the beginning address to start with it .
try to use glVertexPointer w/o the rest as beginning and tell us what happens.

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glVertexPointer(3,GL_FLOAT,sizeof(SVertex),vertices[0].pos);

make it

glVertexPointer(3,GL_FLOAT,sizeof(SVertex), &vertices[0].pos);

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Thank you all for the replies!

Quote:
 GL_INDEX_ARRAY and glIndexPointer are for color-indexed rendering (as in for 8-bit palette displays), not indicies into the vertex array. I agree -- the names are misleading :)First try taking those two lines out and see what happens. Odds are since both the GL_COLOR_ARRAY and GL_INDEX_ARRAY are enabled, there's probably an error being thrown by glDrawElements.

OK, so I removed the indexed color stuff, and it still isn't drawing anything. So then I tried commenting everything but the stuff for vertices and the draw elements function. Still no success.

This is my SVertex structure for those wondering:
	typedef struct	{		struct {			float x,y,z;		}pos;		struct {			float x,y,z;		}normals;		struct {			float u,v;		}uv;		struct {			unsigned char r,g,b,a;		}color;	}SVertex;

Thanks! Rating++

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Hrm, the code looks right... I can't think of any other reason why what you have shouldn't work.

The other thing you could try is using glArrayElement between a glBegin/glEnd pair, instead of the glDrawElements call, like so:

glBegin(GL_TRIANGLES);for (int t = 0; t < triangleCount * 3; t++)    glArrayElement(indices[t]);glEnd();

Trying this will at least determine if your problem is setting up the pointers to the data properly, or the indices being passed to glDrawElements. Another possibility is an error is being thrown somewhere. Stick in a few calls to glGetError() within the code there and make sure it's returning GL_NO_ERROR.

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IMO you should redo the struct and not nest them.

Do something like this
struct Vertex{float vx;float vy;float vz;float nx;float ny;float nz;float s;float t;unsigned char r,g,b,a;};

Keep it simple due to their is no need to nest struct inside of structs.

This way you can do
vertex.vx; ect... and you will be able to interleave them easier IMO... HTH

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OK, I'll try that! Thanks!
Rating++

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OK, I've tried that, and I even tried writing a class that uses Direct3D. Neither draw the model so I'm getting convinced that something really isn't right here.

Edit: I figured I should do one last debug run tonight, and in the corner of my eye I say an error with the "DirectX debug output" that said "invalid number of vertices", so I debugged a little further and somehow I forgot to put the correct number of vertices into the mesh class I have. It draws in OpenGL now, however not in DirectX.

Thank you all for the help! My problem here is solved.

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So glArrayElement with glBegin/glEnd didn't work? Are you getting any GL errors at all?

The only other thing I can think of is your vertex data is broken. You said in your first post that you verified it, but you might want to go in with a debugger and step through line by line double- and triple-checking your data.

As a final case, you can parse your data directly, use glBegin/glEnd and look up the indices yourself in a loop, sending the vertex data to glVertex3f and glColor4ub (and whatever is needed to draw your polygon).

Finally, it might be a good idea just to try vertices *only*, then when that's working, add color, test again, then add texture coords, etc. From what it looks like you're sending normal data but your lights may not be even setup properly. You could be getting a black triangle for all I know. :) (Actually, a good idea is to set your clear color to something other than black to check for black triangles.)

Good luck!

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